1. Field of the Invention
The present invention relates to a control device of a printing apparatus which can automatically change between a plurality of operation modes having their respective control code systems different from each other.
2. Description of Related Art
Various kinds of printing apparatuses are in use in which, letters, figures and the like based on printing data input from an external device are printed in accordance with control codes, such as bold face, subscript, line feed, form feed and the like, contained in the printing data.
In addition, in order to enable more varied printing, known printing apparatuses often have their own particular operation modes such as a high-speed mode for carrying out printing at high speed, a switching mode for switching between lateral writing and vertical writing, a mode for designation of dot space and bit image and the like. These modes are also designated by the control codes, in particular, escape control codes (ESC sequence code) in the printing data. A sequence of printing data input from the host computer has control codes in accordance with an operation mode.
A printing apparatus having a plurality of operation modes and capable of changing the operation modes in accordance with the printing data input from the host computer carries out the following printing operation. First, the input printing data is stored temporarily, and control codes which are particular to each operation mode are detected from the printing data. Then, an operation mode which corresponds to the printing data to carry out a printing operation is determined based on the detected control codes. The determined operation mode is set automatically to carry out the desired printing operation.
However, in the above-mentioned printing apparatus, if no control code exists in the input printing data, an operation mode which corresponds to the printing data to carry out a printing operation cannot be determined at all. Moreover, if each of the detected control codes corresponds to a plurality of operation modes, the degree of certainty to determine one operation mode which best corresponds to the printing data to carry out the printing operation becomes extremely low.
In the above-mentioned cases, there is a high possibility to misjudge an operation mode to carry out a printing operation. As a result, a precise printing result cannot be obtained.